The invention relates generally to the confinement of gases and, more particularly, to the filling of gas cylinders. Of special interest is the filling of gas cylinders which contain a solvent for the gas to be stored and store the gas in at least partially dissolved state.
In the known methods of filling gas cylinders, a specified number of cylinders to be filled are connected to a gas distribution network. Once the cylinders have been connected, gas to be stored is conveyed along the gas feed line to the distribution network by means of a compressor or compressor group. For cylinders of the type which store gas in at least partially dissolved state, a solvent is provided in each cylinder prior to the filling process. During the dissolution process of the gas in the individual cylinders, a quantity of heat is generated which is proportional to the rate of dissolution. This heat causes an increase in the temperature of the solvent, particularly at the solvent-gas interface, and, as a result, the dissolution process, which is substantially temperature dependent and the rate of which decreases with increasing temperature, is slowed. Thus, the time required for filling a cylinder is lengthened.
Moreover, in analogy with the methods used for filling cylinders with compressed gas, the gas pressure in the distribution network is generally increased gradually from an initial value to a final value without taking into account the temperature of the cylinder so that it is possible for the cylinder to become overcharged due to the above-outlined effect. If, because of the above-outlined effect, the cylinder becomes overcharged, that is, the capacity of the cylinder is exceeded, it is possible for the temperature and the pressure in the cylinder to exceed the permissible engineering safety limits which may lead to disastrous consequences.
Attempts have been made to overcome the foregoing disadvantages. Thus, it is known to cool cylinders with ambient air in order to remove the heat generated by the dissolution process and thereby increase the rate of the dissolution process and, concomitantly, reduce the time required for filling the cylinders. However, this has not been satisfactory. Later attempts which have been used in practice to increase the rate of the dissolution process and decrease the filling time have been primarily directed to more rapid removal of the heat generated by the dissolution process than can be realized with air-cooling. These attempts have involved subjecting the cylinders to more intensive cooling such as, for instance, the utilization of cooling water, fluid colloidal systems and freezing mixtures to convey heat from the exterior surfaces of the cylinders. None of these attempts have, however, led to satisfactory results.
The conventional manner of filling cylinders of the type under discussion, that is, connecting a large number of cylinders with a gas feed line and increasing the line pressure during the filling operation until the cylinders are completely filled, possesses another disadvantage aside from the safety factors involved and the fact that the filling time is dependent upon the absorption time, which latter is quite long. This resides in the fact that it is not possible to connect an empty cylinder to the gas feed line while the filling operation is in progress. This has adverse economic implications by virtue of the time lost when a cylinder is ready to be filled but cannot be connected to the gas feed line and by virtue of the lost, non-productive space occupied by the empty cylinder while waiting to be filled.
In general, it has been found that the economy and safety of conventional filling plants can be improved.